Wireless communication systems have been developed to support higher data rate in order to meet the ever-increasing demand for wireless data traffic. For an increase in data rate of the wireless communication systems, technology development has been carried out based on communication technologies such as Code Division Multiple Access (CDMA), Orthogonal Frequency Division Multiple Access (OFDMA) and Multiple Input Multiple Output (MIMO), mainly to improve the spectral efficiency. However, the surging demand for wireless data traffic may not be fully met only with these spectral efficiency improvement technologies.
Recently, the increasing demand for smart devices such as smart phones and tablet PCs and the explosive growth of applications that operate on the smart devices and require a lot of traffic have further accelerated the demand for wireless data traffic. One way to meet these demands is to use more frequency resources over a wider frequency band. Therefore, in order to secure a wider frequency band and apply it to wireless mobile communication, it is necessary to consider securing ultra wideband frequencies in a higher frequency domain.
Wireless communication in a millimeter Wave (mmWave) band may suffer from an increase in propagation loss such as a path loss and a return loss due to the frequency characteristics of the mmWave band. As a result, the range of radio waves is reduced causing a decrease in coverage. On the other hand, the wavelength is very short due to the frequency characteristics of the mmWave band, making it easy to apply beamforming that uses a plurality of small antennas. Accordingly, it is possible to seek new ways to increase the range of radio waves and expand the coverage by mitigating the path loss of radio waves by applying beamforming technology to mmWave-band wireless communication.
Transmit beamforming is generally a way to increase the directivity by concentrating the reach areas of radio waves in a specific direction using multiple antennas. Collection of the multiple antennas is referred to as an antenna array, and each antenna included in the array is called an array element. The antenna arrays may be classified into various types including a linear array and a planar array. Use of transmit beamforming may contribute to an increase in the transmission distance due to the increase in directivity of signals, and since almost no signal is transmitted in directions other than a specific direction, transmit beamforming may remarkably reduce signal interference to users other than a specific user.
On the other hand, a receiver may also perform beamforming on received signals using a receive antenna array. This receive beamforming may also increase the sensitivity of received signals incoming in a specific direction by concentrating received radio waves in a specific direction, and block interference signals by excluding signals incoming in directions other than the specific direction from the received signals.
The conventional cellular system basically considers isotropic or omni-directional transmission/reception between a BS and MSs without applying beamforming to control channels that use a small amount of resources. Therefore, the existing researches on the operation of control channels mainly include defining Hybrid Automatic Retransmission reQuest (HARQ) timing rules, which are determined considering the time required for processing of HARQ data, for an Acknowledgement (ACK) Channel (ACKCH) which is a control channel for transmitting Acknowledgement & Non-acknowledgement (ACK/NACK) which is decoding result information about HARQ data; allocating an HARQ feedback resource area; and mapping ACKCHs within the allocated HARQ feedback resource area.
However, in the wireless mobile communication system using the mmWave band, it is necessary to apply beamforming even to UL/DL control channels for the performance improvement and coverage expansion in a beamforming-based operation for overcoming the significant propagation loss and penetration loss which occur due to the channel propagation characteristics of the mmWave band. Therefore, there is a need for technology for effectively applying UL/DL beamforming to UL/DL control channels such as Uplink Ranging Channel (UL RNGCH), UL Feedback Channel (UL FBCH), and DL/UL HARQ FBCH (DL/UL HFBCH), for the additional performance improvement and coverage expansion in the beamforming-based wireless communication system.